Oxygen concentrators have long been used to provide highly concentrated oxygen to medical patients and for other applications. These devices normally employ a pair of molecular sieve filter tanks that remove nitrogen from the air and produce a highly concentrated oxygen supply for the patient. For example, see the concentrator and accompanying sieve tanks disclosed in U.S. Pat. No. 5,166,563. Conventional concentrators typically require either a pair of 3-way valves or a single 4-way valve to integrate the concentrator pump with the molecular sieve tanks. These valves require a fairly complicated construction, which includes numerous hoses, clamps and fittings. This adds considerably to the cost, bulk and weight of the system. Moreover, such valves tend to exhibit leaks, which can render the entire concentrator useless. As a result, most concentrators experience considerable "down time" in order to undergo necessary repairs.
The valves used in conventional oxygen concentrators are typically timer driven. The required timing mechanisms further increase the cost and complexity of most concentrators. Moreover, known concentrators are often far less than optimally efficient.